NaODFB基复合电解液钠离子电池的电化学性能及其电极/电解液界面研究

Sodium-ion battery is one of the most promising technology for large-sacle energy storage due to the natural abundance and the similar chemistry of these alkali metals of lithium ion battery know-how can, in general, be foreseen. The role of the electrolyte should not be neglected as it is largely responsible for the electrochemical performance and safety. However, the electrolytes for sodium-ion battery are given much less attention than the electrode. The two most common electrolytes used are NaClO4 and NaPF6 solutions in carbonates solvents, which occurs serious safety issue. The project is intended to systematically optimize sodium difluoro(oxalate)borate (NaODFB) based electrolytes. The ion conductivity and sodium transference number will be enhanced by , which is made by varying the constituents of the electrolyte, including solvents, Na-salts, and their respective ratios. The mechanism improvement on cycle stability of electrode (positive electrode and negative electrode) by NaODFB-based electrolytes will be proposed. The influence of electrolyte/electrode interface film components on interface film structure and performance as well as sodiation/desodiation will be investigated. The cycle performance and safety of NaODFB-based sodium-ion battery will be further improved by the selected electrolyte additives. The full cell will be assembled with positive electrode and negative electrode as well as NaODFB-based electrolyte. And performance of the full cell will be further improved to develop a practical sodium ion battery. The results of this project will enhance the superiority of our country in sodium ion battery electrolyte research fields and provide application foundation to construct clean and low-cost energy storage system.

钠在地壳中储量丰富，由于钠与锂化学性质相似，钠离子电池在大规模储能中具有广阔的应用前景。电解质是电池的重要组成部分之一，对电池的电化学性能及安全性能均有很大影响。目前对钠离子电池电解质的研究甚少。主要的电解质为NaClO4或NaPF6的碳酸酯溶液，这二者均存在安全问题。本项目拟系统研究并优化NaODFB基电解质：从溶剂、混合溶质方面提高电解液的离子电导率及钠离子迁移数；研究NaODFB基电解质对对正负电极循环稳定性影响的机理；阐明界面膜的组分对界面结构与性质及对钠离子脱嵌过程的影响规律；筛选电解液添加剂以进一步改善NaODFB基钠离子电池的循环性能和安全性能；将正负极与电解质体系组装钠离子全电池，并对全电池性能进行改善，开发出性能优良的钠离子电池。加强我国在钠离子电池电解液技术这一新领域的研究优势，为构建清洁、低成本的钠离子储能及动力电池及其应用奠定一些基础。

钠在地壳中储量丰富，由于钠与锂化学性质相似，钠离子电池在大规模储能中具有广阔的应用前景。电解质是电池的重要组成部分之一，对电池的电化学性能及安全性能均有很大影响。目前对钠离子电池电解质的研究甚少。主要的电解质为NaClO4或NaPF6的碳酸酯溶液，这二者均存在安全问题。本项目基本按照研究计划进行：系统研究并优化NaODFB基电解液；研究NaODFB基电解质对正负极材料循环稳定性影响的机理；阐明界面膜组分对界面结构与性质及对钠离子脱嵌过程的影响规律。结果表明，NaODFB/PC电解液中金属钠的沉积溶出效率最高，钝化电位较低，循环稳定性最好，NaODFB/PC电解液安全性（阻燃性）优于NaClO4/PC或NaPF6/PC电解液。NaODFB对富锂三元正极材料及Na3V2(PO4)3正极材料的容量及循环稳定性都有显著增强的效果，富锂三元正极材料在NaODFB/PC电解液中0.5 C循环200次，容量151 mAh∙g-1，同样条件，在NaClO4/PC电解液中循环50次，容量迅速衰减；在1 C电流密度下，分别于1 M NaODFB/PC、NaClO4/PC或NaPF6/PC电解液中，充放电循环1000次后，Na3V2(PO4)3电极在1 M NaODFB/PC的电解液中的循环性能最稳定，放电比容量最高，为75.3 mAh∙g-1。通过分析固态电解质相界面（SEI）组成对富锂三元材料及Na3V2(PO4)3电极材料的影响，表明在1 M NaODFB/PC电解液中循环后形成的SEI膜很稳定，且利于钠离子的嵌入脱出，并且可以有效缓解由于钠离子的嵌入脱出引起的体积膨胀。项目组多种渠道获得的硬碳负极材料在NaClO4、NaPF6或NaODFB的电解液中的容量都迅速衰减，为了寻找合适的钠离子电池负极材料，项目组进行了一些拓展研究，并取得了一些成果。截至目前为止，以第一或通讯作者发表SCI论文9篇，申请国家发明专利3项，已授权2项，参加国内会议2次，发表会议论文3篇，利用所取得的研究成果指导学生参加团中央、教育部等联合举办的 “挑战杯”中国大学生创新创业计划大赛2次，获得1项国家铜奖，1项江西省金奖，1项江西省银奖。培养研究生3名，本科生8名。